Method of pouring molten metal

ABSTRACT

A molten metal pouring method and apparatus for use with a continuous metal casting machine wherein molten metal is poured from a pouring vessel through a pouring spout into an arcuate mold formed by the peripheral groove of a casting wheel and a continuous band surrounding a portion of the casting wheel. The pouring spout is formed with a passage having a reduced diameter at its outlet opening, and the molten metal is initially flowed at a high flow rate to purge substantially all of the air from the internal passage of the pouring spout, and pool the metal in the larger diameter portion of the pouring spout. The absence of air in the pouring spout is effective to reduce voids and blisters in the cast bar and the build up of solidified metal in the internal passage of the pouring spout.

United States Patent [191 Richardson METHOD OF POURING MOLTEN METAL [75]Inventor: Billy Joe Richardson, Carrollton, Ga.

[73] Assignee: Southwire Company, Carrollton, Ga.

[22] Filed: Jan. 20, 1971 [21] Appl. No.: 107,917

Related US. Application Data [62] Division of Ser. No. 809,241, March21, 1969,

FOREIGN PATENTS OR APPLICATlONS Great Britain 164/278 51 July 17,1973

Primary: ExdminerR. Spencer Annear Attorney-l-lerbert M. Hanegan [57]ABSTRACT A molten metal pouring method and apparatus for use with acontinuous metal casting machine wherein molten metal is poured from apouring vessel through a pouring spout into an arcuate mold formed bythe peripheral groove of a casting wheel and a continuous bandsurrounding a portion of the casting wheel. The pouring spout is formedwith a passage having a reduced diameter at its outlet opening, and themolten metal is initially flowed at a high flow rate to purgesubstantially all of the air from the internal passage of the pouringspout, and pool the metal in the larger diameter portion of the pouringspout. The absence of air in the pouring spout is effective to reducevoids and blisters in the cast bar and the build up of solidified metalin the internal passage of the pouring spout.

3 Claims, 3 Drawing Figures Patented July 17, 1973' I 7 3,746,072;

2 Sheets-Sheet 1 i BILLY JOE RICHARDSON VAN C. WILKS BY H. M. HANEGANATTORNEYS Patented July l 7, 1973 R 3,746,672

2 Sheets-Sheet 2 PRIOR ART INVENTOR BILLY JOE RICHARDSON VAN C. WILKS H.M. HANEG'AN ATTORNEYS METHOD OF POURING MOLTEN METAL CROSS-REFERENCE TORELATED APPLICATIONS This is a division of copending application Ser.No. 809,241, filed Mar. 21, 1969, now abandoned.

BACKGROUND OF THE INVENTION A typical casting machine for continuouslycasting metal comprises a rotatable casting wheel defining a peripheralgroove, a flexible band surrounding a portion of the casting wheel anddefining with the peripheral groove an arcuate mold, a pouring vesselpositioned adjacent the arcuate mold, and a pouring spout extending fromthe pouring vessel toward the arcuate mold. The molten metal flows fromthe pouring vessel through the pouring spout into the arcuate mold, andthe casting wheel continuously rotates to carry the molten metal fromthe entrance to the exit of the arcuate mold. Coolant is applied to theexternal surfaces of the casting wheel and flexible band to extract theheat from the molten metal which results in solidifying the moltenmetal, and the solidified metal is extracted from the peripheral grooveof the casting wheel as the metal reaches the end of the arcuate mold.

During the operation of the casting machine the rotational speed of thecasting wheel and the flow of metal from the pouring vessel to thearcuate mold are controlled by the machine operator or by an automaticcontrol system to maintain a level or pool of molten metal in thearcuate mold. When the casting machine is first placed in operation, thecasting wheel is usually rotated at a slow speed and the metal is pouredat a relatively high rate of flow from the pouring vessel until the poolof metal is established in the arcuate mold and the lead end of the castbar has been extracted from the casting wheel and led to the rollingmill or other subsequent processing equipment. When the pool of moltenmetal has been properly established and the equipment is ready forhigher capacity operation, the operator increases the rotational speedof the casting wheel and adjusts the flow of molten metal tocontinuously maintain the pool of molten metal in the arcuate mold.After the higher capacity casting has been established, the main controlfunction of the operator is achieved by adjusting the flow of moltenmetal from the pouring vessel into the arcuate mold. This is usuallyaccomplished with the metering pin which varies the opening between thepouring vessel and the pouring spout, and results in more or less moltenmetal flowing through the pouring spout.

When molten metal flows from the pouring vessel through the pouringspout into the arcuate mold formed by the casting wheel and the flexibleband, the pouring spout is usually not fully occupied with molten metal;that is, an air gap is usually present in the pouring spout between theflowing metal and the inner surface of the passageway through thepouring spout. When the flow of metal is increased through the pouringspout some of this air is displaced by the additional volume of metaland forced through the outlet of the spout. When the outlet of the spoutis submerged in the pool of molten metal in the arcuate mold, the airforms bubbles in the molten metal which are frequently carried with themolten metal as it is cooled and solidified into a cast bar. Also, whenthe flow of molten metal through the pouring spout is reduced, thedecreasing volume of flowing metal in the pouring spout creates areduced pressure in the accompanying air gap in the spout. This reducedpressure frequently causes air to bubble up through the outlet openingof thepouring spout if the outlet opening of the pouring spout everbreaks the surface of the pool of meta] formed in the arcuate mold.Thus, bubbles are again created in the flowing metal, which are likelyto be carried with the flowing metal as-it travels about the castingwheel.

When the molten metal is subsequently cooled and solidified, the bubblesappear as internal voids or surface blisters in the cast bar. Thesevoids and blisters weaken the bar so that when the bar is extracted fromthe casting wheel it is more likely to split or crack. When the cast barpasses to a rolling mill, the blisters and voids may not be worked outof the metal as the metal is worked in the rolling mill and may passwith the metal as it is formed into rod. Of course, these imperfectionsin the rod cause poor grain structure and form a weaker rod. As the rodis further processed into wire by drawing, the rod or wire is likely tobreak during the drawing process.

During the normal operation of a casting machine there is a gradualbuild up of solidified metal on the surfaces of the internal passage ofthe pouring spout. This build up of solidified metal results from themolten metal cooling inside the pouring spout before it reaches thearcuate mold. While the temperature of the molten metal leaving thepouring vessel is usually high enough above its solidificationtemperature to pass through the pouring spout without solidfying, theentire surface of the pouring spout is not contacted by the moltenmetal, but is partially contacted by air, so that the heat from themolten metal does not maintain the entire body of the pouring spout at atemperature above the temperature of solidification of the molten metal.Thus, when the flow of metal through the pouring spout decreases orshifts from one surface of the pouring spout passageway to anothersurface of the passageway due to flow turbulence, machine vibrations,etc., the residue of metal left on the first surface is left to cool asthe air is displaced around the passageway, and the residue of metalsolidifies and clings to the passageway of the pouring spout. When theflowing metal again shifts back to its original position, the solidifiedresidue has formed a new surface in the passageway of the pouring spout,and the residue of metal left on the second path of metal flow on thesurface of the passageway also begins to cool and eventually solidifies.As the flow of molten metal continues to increase and decrease and toshift within the passageway of the pouring spout, the solidifiedresidues eventually build up and reduce the internal cross-sectionalarea of the passageway, which reduces the flow capacity of the pouringspout. Eventually, the flow capacity of the pouring spout is reduced toa level that is not sufficient for proper operation of the castingmachine; that is, when the operator withdraws the metering pin so as toachieve maximum flow of molten metal from the pouring vessel to thearcuate mold, the capacity of the pouring spout is not sufficient tomaintain the pool of molten metal in thecasting wheel. The operator thenmust reduce the rotational speed of the casting wheel to maintain thepool of molten metal, and this results in lower capacity casting.

SUMMARY OF THE INVENTION Briefly described, the present inventioncomprises a method and apparatus for pouring molten metal in acontinuous casting system which eliminates air flow from the pouringspout into the pool of metal in the casting machine, eliminates thebubbles in the molten metal and the resulting voids and blisters in thecast bar, and prevents the build up of solidified metal within thepassageway of the pouring spout from reducing the flow capacity of thepouring spout. The pouring spout is formed with a reduced diameterpassageway at its exit opening, and the operator initially flows themolten metal at a high rate of flow to purge substantially all of theair from the passageway of the pouring spout and pool the molten metalin the larger diameter portion of the pouring spout passageway. When theflow of molten metal through the pouring spout is reduced, the smallerdiameter exit opening of the pouring spout will remain submerged belowthe pool of metal to form a liquid seal such that no air will flow ineither direction through the smaller diameter portion of the passageway.In this manner, molten metal is maintained in contact with the entiresurface of the smaller diameter portion of the passageway of the pouringspout at all times, which prevents the displacement of any air throughthe pouring spout passageway and prevents the build up of solidifiedmetal in this portion of the passageway.

Thus, it is an object of this invention to provide a molten metalpouring method and apparatus that eliminates voids and blisters fromforming in the cast bar.

Another object of this invention is to provide a molten metal pouringmethod and apparatus for a continuous metal casting machine whichprevents the build up of solidified metal within the pouring spout ofthe casting machine.

Another object of this invention is to provide a pouring spout for acontinuous metal casting machine that maintains substantially constantflow rate capacity throughout the entire casting operation of thecasting machine.

Other objects, features and advantages of the present invention willbecome apparent upon reading the following specification, when taken inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial sidecross-sectional view of a pouring vessel, a pouring spout and a castingwheel, with parts broken away for clarity.

FIG. 2 is a partial side cross-sectional view of a pouringspout, showinga modified pouring spout.

FIG. 3 is a partial side cross-sectional view, similar to FIG. 1, butshowing a prior art continuous casting system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in more detail tothe drawing, in which like numerals indicate like parts throughout theseveral views, FIG. I shows a portion of a casting machine whichincludes casting wheel 11, flexible band 12, pouring vessel 13, andpouring spout assembly 14. Casting wheel 11 defines a peripheral groove16, and flexible band 12 moves with casting wheel 11 in the direction asindicated by arrow 17, and forms arcuate mold 18. Band 12 is guided awayfrom peripheral groove 16 at another point about the casting wheel 11(not shown) to open arcuate mold 18. Pouring vessel 13 is displaced tothe side of casting wheel 11 and pouring spout assembly extends frompouring vessel 13 over the intersection of the band and the castingwheel to guide molten metal from the pouring vessel to the mold.

Pouring vessel 13 has concave or sloped bottom walls 19 which define anoutlet opening. Pouring spout assembly is T-shaped and includes T-shapedconnecting pipe 20 which has its base leg inserted into the outletopening of the pouring vessel and extends over the mold, pouring spout21 which projects into the mold, and vent tube 21a which extends awayfrom the pouring spout. Pouring spout 21 defines passageway 22throughout its length, and passageway 22 includes inlet opening 23 whichopens into connecting pipe 20 and outlet opening 24 which opens intoarcuate mold l8. Passageway 22 is tapered at 25 which divides passageway22 into upper or inlet end 26 and lower or outlet end 27. Outlet end 27is of smaller cross-sectional area or diameter than inlet end 26. Inletend 26 of'passageway 22 is of constant cross-sectional area and extendsalong a major portion of pouring spout 21 while outlet end 27 is also ofconstant cross-sectional area. The external surface of pouring spout 21is of constant diameter from inlet opening 23 toward the tapered portion25 of passageway 22, and then is tapered to a smaller diameter at outletopening 24. Thus, the thickness of the annular wall surroundingpassageway 22 is generally constant throughout the entire length ofpouring spout 21.

FIG. 2 shows a modified pouring spout 29, which has a passageway 30 witha gradual tapered portion 31. The remaining dimensions and shapes ofpouring spout 29 are essentially the same as those of pouring spout 21.

OPERATION When operating the prior art pouring equipment as shown inFIG. 3, the metering pin (not shown) is withdrawn from the donut whichleads to pouring spout assembly 37 to create a flow 39 of molten metalfrom the pouring vessel to the arcuate mold of the casting machine. Theinternal passageway of the pouring spout 38 is of constantcross-sectional area throughout its entire length, and when the meteringpin is withdrawn so as to completely open communication between thepouring vessel and the pouring spout assembly to create a maximum metalflow through pouring spout 38, the acceleration of the metal flow 39 dueto the effects of gravity will cause the diameter of the metal flow atthe outlet opening 40 of pouring spout 37 to be smaller than thediameter of the metal flow at the inlet opening 41. The flowing metalclings to the internal surface of the passageway, and an air gap 42extends up the passageway from outlet opening 40 to a position where theentire passageway of the pouring spout is occupied by the stream ofmetal.

Due to adjustments in the position of the metering pin, the turbulenceof the flowing metal 39, the vibra tion of pouring spout 38, and otherfactors, the flowing metal frequently changes position within thepassageway of the pouring spout 38, and clings to a different surface ofthe passageway from time to time. When the flowing metal 39 shifts to adifferent position within the passageway, the surface from which itshifts is left with a residue of metal. This residue clings to thesurface of the passageway and cools, and eventually solidifies if theflowing metal does not shift back to the residue to maintain itstemperature above its temperature of solidification. After the moltenmetal shifts a number of times and the different residues of moltenmetal have been allowed to solidify, the effective opening of thepassageway will begin to choke up or close, which reduces the flowcapacity of pouring spout 38. Eventually the build up of solidifiedmetal in the passageway will be sufficient to reduce the flow capacityof the pouring spout to a level below that sufficient for the operatorto maintain the pool of metal in the arcuate mold of the castingmachine, and the smaller capacity flow of molten metal through thepouring spout will have to be compensated for by a reduction in speed ofthe casting wheel. Of course, this reduces the capacity of the castingmachine, and the pouring spout must eventually be replaced.

Moreover, when the metering pin in the pouring vessel is adjusted toincrease the flow of metal through pouring spout 38, the increasedvolume of flowing metal causes a displacement of air from the pouringspout. If the outlet opening is properly submerged inthe pool 19 ofmetal, the air forms bubbles 43 in the molten metal which are frequentlycarried with the molten metal in the areuate mold, and when the metalsolidifies the bubbles appear as internal cavities or surface blistersin the cast bar. When metering pin is adjusted to decrease the flow ofmetal through pouring spout 38, the reduced volume of flowing metal inthe pouring spout causes a reduction of pressure in air gap 42 whichtends to increase the size of air gap 42 and bubble air into the pouringspout when the outlet 40 of the spout breaks the surface of pool 19.This flow of air also tends to form bubbles in the flowing metal andresults in internal cavities and surface blisters appearing in the castbar. Also, a reduction in metal flow through the pouring spout leaves ametal residue on the surface of the passageway which eventuallysolidifies.

As is shown in FIG. 1, the opening of passageway 22 of pouring spout 21is reduced at its outlet opening 24. When the operator of castingmachine establishes a flow of molten metal through the pouring spout,the metering pin is opened wide to establish a maximum flow, to purgesubstantially all of the air from passageway 22. After the air has beenpurged, the metering pin is adjusted to establish the proper flowrelationship with the casting wheel. The dimension of outlet portion 27of passageway 22 will not allow air to pass up into passageway 22through outlet opening 24. The dimension of inlet portion 23 ofpassageway 22 is established so that the pouring friction between thesurface of passageway 22 and the flowing metal is negligible and thisportion of the passageway becomes a reservoir or pool and suppliesmolten metal to outlet portion 27. Tapered portion 25 of passageway 22is shaped so as to allow a smooth transition of metal flow between inletportion 26 and outlet portion 27. Thus, the pooling of the metal in theinlet portion of the spout causes any air in the spout to be displacedupwardly and out vent tube 21a. The pool of metal can also extend upvent tube 21a under maximum flow conditions.

After the flow of molten metal through pouring spout 21 has beeninitially established and virtually all of the air has been purged frompassageway 22, the flowing metal will be under positive pressurethroughout the entire length of passageway 22 when metering pin 32 hasbeen completely withdrawn from its donut to create a maximum openingbetween passageway 22 and pouring vessel 13. This creates a maximum flowfrom pouring vessel 13 to arcuate mold 18 of casting machine 10, and theflow rate of the flowing metal will be determined to some extent by thehead of metal between the surface of the metal in pouring vessel 13 andpouring spout outlet opening 24; that is, if the level of molten metalin pouring vessel 13 is high, the flow rate through pouring spout'2lwill be high and the level of the pool of metal established in pouringspout 21 will be high. When it is desired to reduce the flow ratethrough pouring spout 21, the metering pin is moved toward its donut toreduce the effective opening between pouring vessel 13 and pouring spout21. This increases the friction or turbulence of metal flow and the rateof metal flow from pouring vessel 13, and the level of the pool of metalwithin the pouring spout is reduced, which reduces the effective headand rate of metal flow through the pouring spout. Of course, the mass ofmetal extending from outlet opening 24 toward inlet opening 23 ofpassageway 22 is effective to maintain the flow of metal within pouringspout 21 as long as metal is supplied from pouring vessel 13 topassageway 22 of pouring-spout 21. As the metering pin is moved furtherinto its donut the flow of metal from pouring vessel 13 is furtherreduced and the level of the pool of metal in the pouring spoutdecreases which reduces the head and rate of flow through the pouringspout. When the metering pin is adjusted to increase the flow ofmetal'from the pouring vessel, the pool of metal in the pouring spoutbuilds up and displaces the air above the pool out through the venttube.

If a metal residue builds up on the inner surface of passageway 22 dueto the shifting of the flowing metal and the varying height of the poolof metal, the build up of the metal residue will be isolated to thelarger diameter inlet portion 26 of passageway 22 and will generally notbe effective to reduce the flow capacity of pouring spout 21 for aprolonged period of time, or until the reduction in the flow capacity ofthe larger diameter portion of passageway 22 is below the flow capacityof outlet portion 27 of passageway 22.

The shape of pouring spout 21 and its flow characteristics virtuallyeliminate the possibility of an increasing metal flow rate through thespout displacing air from the spout into the pool of molten metal in thearcuate mold and the hazard of forming bubbles in the molten metal inthe arcuate mold is substantially eliminated by the elimination of airsurging into or out of pouring spout 21. Thus, the hazard of blisters orcavities being formed in the cast product is substantially eliminated.

While this invention has been described in detail with particularreference to preferred embodiments thereof, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention as described hereinbefore and as defined in theappended claims. 2

I claim:

1. A method of pouring molten metal from a pouring vessel into awheel-band type metal casting machine through an inclined spout having arestricted outlet portion, comprising:

initially purging substantially all air from the outlet portion of thespout by flowing the molten metal at a high flow rate which issufficient to substantially fill the interior of the spout with moltenmetal thereby forcing all air contained therein out through the outletopening thereof,

flowing the molten metal through the inclined spout at a rate which willestablish and maintain at least the outlet portion of the inclined spoutsubmerged in a pool of molten metal in the casting machine thereby Iestablishing a liquid seal in at least the outlet portion of theinclined spout,

the liquid seal preventing the flow of any air through the inclinedspout into the pool of molten metal during the pouring operation.

1 g 2. The method of claim 1 wherein the step of establiquid seal.

1. A method of pouring molten metal from a pouring vessel into awheel-band type metal casting machine through an inclined spout having arestricted outlet portion, comprising: initially purging substantiallyall air from the outlet portion of the spout by flowing the molten metalat a high flow rate which is sufficient to substantially fill theinterior of the spout with molten metal thereby forcing all aircontained therein out through the outlet opening thereof, flowing themolten metal through the inclined spout at a rate which will establishand maintain at least the outlet portion of the inclined spout submergedin a pool of molten metal in the casting machine thereby establishing aliquid seal in at least the outlet portion of the inclined spout, theliquid seal preventing the flow of any air through the inclined spoutinto the pool of molten metal during the pouring operation.
 2. Themethod of claim 1 wherein the step of establishing a liquid seal in theinclined spout comprises maintaining the restricted outlet portion ofthe inclined spout completely filled with molten metal during thepouring operation.
 3. The method of claim 1 including continuing thehigh flow rate until at least a portion of the inclined spout issubmerged in the molten metal, and then reducing the flow rate to alevel sufficient to maintain the liquid seal.